Paper products and method of producing same



July 23, 1968 a. CALVERT 3,393,925

PAPER PRODUCTS AND METHOD OF PRODUCING SAME Filed Jan. 29, 1964 INvENTQ BY Am MM 5am a ATToRNEYb United States Patent 3,393,925 PAPER PRODUCTS AND METHOD OF PRODUCING SAME Bertram Calvert, 29-30 Clipstone St., London, England Filed Jan. 29, 1964, Ser. No. 341.084 Claims priority, application Great Britain, Feb. 11, 1963, 5,:379/63 22 Claims. (Cl. 282-24) ABSTRACT OF THE DISCLOSURE A stack of readily separable sets of paper sheets, each including a plurality of sheets edge-adhered together, is formed by stacking sheets with mutually contacting sheet inner surfaces within each set and mutually contacting sheet outer surfaces on the outside of each two adjacent sets in the stack, and applying adhesive to the edge of the stack, the sheet edge portions at the stack edge to which adhesive is applied being free of previously applied adhesive resist and inherently having relative absorbency characteristics such that the adhesive effectively adheres the mutually contacting sheet inner surfaces together and does not adhere the mutually contacting sheet outer surfaces together sufficiently to prevent easy separation of adjacent sets in the stack.

This invention relates to paper and paper products and is applicable to products which are required to adhere edgewise in sets of two or more sheets of paper, such sets frequently being referred to as tip gummed sets.

In this specification the term outer will be used to define the outer sheets of paper when a set of three or more sheets of paper is made-up, and the term inner will be used herein to define the inner sheets of paper in a set thereof.

According to the present invention in a method of forming sets of two or more sheets of paper which are secured together at their edges by means of a nonrubberised adhesive, the sheets for two or more sets are arranged in a stack to the appropriate edge of which the adhesive is applied, and the viscosity of the adhesive and the absorbency of the surfaces of the sheets are arranged so that the adhesive is absorbed into the surface edges of the sheets which are to be joined sufficiently to secure them together, but is not absorbed into the outer surfaces of the outer sheets of each set to such an extent that contacting outer sheets of adjacent sets cannot be easily separated.

Thus, when the adhesive is dry, the outer surfaces of the outer sheets of two adjacent sets will not have stuck together.

Preferably the adhesive is arranged to penetrate beneath the surface into the interior of the edges of at least one of the inner sheets but not into the interior edges of the upper and lower sheets.

The term hard will be used herein to define hard, sized sheets of paper which are normally used by stationery manufacturers for this type of work, and have a cob test of up to approximately 24. Similarly the term soft will be used herein to define soft, sized sheets of paper not normally used by stationery manufacturers and having a cob test of approximately 4040.

When such papers are used the sheets are preferably arranged so that the outer sheets are hard and the inner sheets are made up so that there are no hard sheets which are not separated by soft sheets.

Conveniently the sheets in the set are alternately hard and soft, the outer sheets being hard, alternatively all the inner sheets may be soft and only the outer sheets hard.

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It has been found that with this process the soft surfaces adhere in a suitable fashion to hard surfaces and to each other but the hard surfaces do not adhere to one another. It is therefore convenient to use this process for making up large quantities of sets, but to ensure self separation of the sets of sheets when they are made up, it is necessary that each starts and ends with a sheet having an outwardly facing hard surface which the adhesive will not penetrate.

Thus it sets comprising six sheets of paper are to be made up then the top sheet can be made from hard paper, the second would be made from soft paper, the third sheet also from soft paper, the fourth from hard paper, the fifth from soft paper and the sixth sheet from hard paper. For even numbers of sheets, therefore the collation must include two soft sheets next to one another in each set to ensure starting and ending each set with a hard sheet.

It will be appreciated that the invention can also be carried out if only the surfaces of the sheets have the necessary characteristics and in this specification the term nonabsorbent will be used to define the surface of a sheet of paper, the make-up, fibre and loading content, grain direction, hygroscopic properties, sizing, absorbency, calendering, surface texture, capillary attraction porosity and density, as for example measured. by a Gurley densometer, of which have been so adjusted that, when collated with sheets having absorbent surfaces as defined below and used with a suitable adhesive to carry out the process the adhesive is not absorbed into the surface. The term nonabsorbent will also be used to define the surface of nonabsorbent base paper of the above properties, which may also be covered with a carbon coating which however must not cover the edge which is to adhere to the other sheet or sheets. This paper may be used either as a one-time carbon tissue, carbon-backed paper or spot carbonized paper.

The term absorbent will be used to define the surface of a sheet of paper, the make-up, fibres and loading content, grain direction, hygroscopic properties, sizing, absorbency, calendering, surface texture, capillary attraction absorbency and density, as for example measured with a Gurley densometer, of which have been so adjusted that when collated with a sheet having a nonabsorbent surface as defined above and used with a suitable adhesive to carry out the process, the adhesive is absorbed into the surfaces to enable the sheets to adhere to the surface adjoining it. The term absorbent will also be used to define the surface of absorbent base paper of the above properties, which may also be covered with a carbon coating which must not cover the edge which is to adhere to the other sheet or sheets. This paper may be used either as a one-time carbon tissue, carbon-backed paper or spot carbonized paper.

The makeup, fibre, loading content, hygroscopic properties, sizing, absorbency, calendering, surface texture capillary attraction of the surface porosity, density and grain direction of a paper determine its absorbency and it has been found that when sheets of paper are made up as set forth they are amenable to gluing along their edges for making up into self supporting tip-gummed sets such as are used for invoices with copies, delivery notes, order forms, record forms and catalogues.

Thus, in another preferred form of the invention the sheets are arranged so that the outwardly facing surfaces of the outer sheets are nonabsorbent and the inner sheets are made up so that there are no nonabsorbent surfaces on thesheets which are not separated by sheets with absorbent surfaces.

As in the hard and soft sheets, the sets are made up to provide alternate absorbent and nonabsorbent surfaces between the sheets with the outer sheets having nonabsorbent outer surfaces. Alternatively, all the inner sheets may preferably have absorbent surfaces provided that the outer sheets have outer surfaces which are nonabsorbent.

It has been found that sheets of a given density may be used for inners, or outers, provided that they are collated with appropriate sheets of greater or less density as required.

In a convenient method, the nonabsorbent sheets are provided by sheets having a grain direction which is parallel to the gumming edge, and absorbent sheets are provided by sheets having a grain direction which is normal to the gummin'g edge.

Thus the density of the sheets in each set may be substantially the same.

It has been found however that if sheets of more than one quality are collated together in each set then such sheets should have a Gurley densometer reading of less than 1,000, and a cob test figure of less than 40.

Papers which have been coated, to provide a different surface characteristic, may also not give satisfactory results using grain directions only, as their surfaces will be changed, for example, a wax type coating would repel the adhesive and a clay type coating would absorb it. However if the coating leaves the gumming edge clear the grain direction method may still be applied. In this and other applications, sheets having a Gurley densometer reading of 1,000 or over may be coated with carbon to make up into one time carbon sets.

Thus, these sheets could be collated with other sheets of the same reading by arranging the grain directions as set forth above, or could be collated with other sheets of different readings by relying on differential densities. For example, carbon coated sheets of 1,000 or over would be absorbent if arranged with their grain direction parallel to the gumming edge and were collated with other sheets whose grain direction was for example also parallel to the gumming edge and having a Gurley densometer reading of less than 300.

In any case, the sheets are preferably provided with a watermark to indicate the grain direction and the invention also includes paper sheets for use with the method which carry such a watermark, and to sets made up from such sheets.

The adhesive is preferably applied by brush or by means of an aerosol, and a suitable adhesive for use with the process comprises low viscosity dextrine adhesive comprising for example, 20% dextrine, 60% water and 10% alcohol, borax, 5% china clay or a low viscosity gum arabic with added alcohol china clay.

The invention may be performed in various ways, but some methods will now be described by way of example and with reference to the accompanying drawings in which:

FIGURE 1 shows a collation of sheets of hard and soft papers;

FIGURE 2 shows a collation of sheets having absorbent and nonabsorbent surfaces; and

FIGURE 3 shows a collation of sheets using papers of different grain directions.

Referring first to the use of hard and soft sheets, the sets are produced by first collating each set in the necessary manner, for example if sets of five sheets are to be made up they will be stacked with the paper in the order hard, soft, hard, soft, hard and a large number of such collations will be stacked on top of one another. In the arrangement of sheets shown in FIGURE 1 three sets are shown stacked on top of each other, each set comprising three sheets. The top set of three sheets comprises a 'hard outer sheet 1, a soft inner sheet 2 and a hard lower outer sheet 3. The same reference numerals are used to indicate the sheets of the second and third sets and as will be seen the outer surfaces of the top and bottom sheets of each set face a hard sheet.

After guillotining the edges to be secured together the stack is piled on a bench under a weight of approximately 20 lbs. or placed in a press, and an adhesive is applied to the opposed face edges of the stack of elements by brushing, or by the use of an aerosol. In FIG- URE an aerosol 4 is indicated. The adhesive comprises 20% detxrine 60% water and 10% alcohol, 5% borax, and 5% china clay or a low viscosity gum arabic adhesive with added alcohol and china clay. This adhesive will penetrate the edges for about of an inch, drying inwards from the outer surface of the stack. When the adhesive has completely dried a period of about 15 minutes, which may vary considerably according to the humidity and temperature of the room, the individual sheets of the respective sets will be found to be stuck fast at the edge; and without further operation the sets will have separated from one another. For sets which are to be made with one-time carbon collated between each sheet of each set and comprising three or more sheets in each set, the carbon paper must be manufactured from a soft paper before coating with carbon and the edge which is to be secured must be free from the carbon coating. It will be found that the adhesive will penetrate the soft uncarbonized edge of the carbon paper in the same manner as set forth above, causing the sheets to adhere in sets and to separate between sets.

When sheets with absorbent and non-absorbent surfaces as herein defined are used, the sets can be produced by first collating each set in the necessary manner, for example if sets of 5 sheets are to be made up they will be stacked with the paper in the order two sheets with non-absorbent surfaces as outers and three sheets with absorbent surfaces for the inners. In the arrangement shown in FIGURE 2, sheets with absorbent and nonabsorbent surfaces are shown which have been made up into sets of three. With this collation the upper outer sheet 5 of each set is arranged with its outer surface 5a to be nonabsorbent and its inner surface can be absorbent or nonabsorbent, the inner sheet 6 is arranged to be absorbent on both surfaces, and the lower sheet 7 is arranged to have an outwardly facing surface 7:: which is nonabsorbent and its inner surface absorbent or nonabsorbent. As described with reference to FIG- URE 1 the sets are arranged on top of one another and in this case the nonabsorbent surfaces on the second and third sets are indicated by the reference numerals 8 and 9 respectively. An aerosol 10 is also shown and the sheets may be secured together in a similar manner to that described with reference to FIGURE 1. The drying time for any of the sets can take from 15 minutes in a Warm dry atmosphere with infra red or warm convected air blowing onto the stack or by placing near a heater, up to 4-5 hours in a cold damp atmosphere and even longer in extreme, humid conditions.

When sets are to be made up with absorbent and nonabsorbent surfaces and one-time carbon tissue is to be collated, the carbon paper can be manufactured from, for example absorbent tissue with a Gurley densometer reading of 1,000 and the other sheets arranged to have appropriate densities, the edge of the sheet which is to be secured being of course free from carbon coating. Thus a carbon coated sheet of 1,000 or over would be absorbent if arranged with its grain direction parallel to the gumming edge and was collated with non-absorbent sheets when grain direction was also parallel to the gumming edge and the Gurley densometer reading of which was less than 300.

It is possible to use a particular sheet as the outer for one collation and that same sheet as an inner for another collation. The factors governing this are the make-up, fibre and loading content, hygroscopic properties, sizing, absorbency, calendering, surface texture capillary attraction porosity, density and grain direction of the surfaces of the sheets which make them respectively absorbenf or nonabsorbent in relation to the other sheets.

Sheets required for collating into sets may be coated either over-all or at the tipping edge only by hand or machine after the paper has been made, prior to collation, to achieve similar results and a wax substance could be used for the outer surfaces of each set, or alternatively an adhesive agent for the inner surfaces of each set.

It has been found that sheets may be prepared with a loading of china clay, the untreated surfaces of such sheets being nonabsorbent and suitable as outer surfaces, and absorbent surfaces being provided by calendering surfaces concerned.

In the method illustrated in FIGURE 3 the sheets are arranged with their grain directions in a particular order so that edge adhesion is obtained as required. In this arrangement nonabsorbent sheets are provided by sheets 11 having a grain direction, indicated by the arrows, which is parallel to the gumming edge. The absorbent sheets are provided by sheets 12 having a grain direction, also indicated by arrows, which is normal to the gurnming edge.

The outer sheets 11 do not stick to each other but only to the inner sheets which have the normal grain direction.

This method of arranging the sheets is particularly useful as it enables sheets of the same type and density to be secured together in sets.

If required, sheets can be prepared in which the grain direction is indicated by a suitable watermark, which will assist in collating the sheets when making up sets.

It will be appreciated that in the methods described in relation to FIGURES l and 2 the grain direction may not be of importance provided the other factors are arranged to provide the required adhesion between the sheets, for example sheets may be collated all having their grain running parallel to the gumming edge and containing outers having a Gurley densometer reading of up to 300 and with inners of 1,000 or over and satisfactory sets will be obtained. Similarly, if those inners are interleaved with single sheets having readings of up to 300 the sets will still be satisfactory.

At the present time it is customary for printers to collate papers into sets, fan the edge to be tip-gummed, apply an adhesive to that edge and close the fan. When dry the sheets are then parted in their respective sets with a steel blade. This invention avoids the necessity for fanning and slitting the sets, thereby saving 90% of the time normally required for this operation.

I claim:

1. A stack of readily separable sets of paper sheets, each set including a plurality of sheets edge-adhered together, there being mutually contacting sheet inner sur faces within each set and mutually contacting sheet outer surfaces on the outside of each two adjacent sets in the stack, said mutually contacting inner and outer surfaces being free of applied coating of adhesive resist; and an application of adhesive on one edge of said stack, the mutually contacting sheet inner surface edge portions. at said edge of said stack being relatively absorbent of said adhesive whereby said adhesive effectively adheres said sheet inner surface edge portions together, and the irnutually contacting sheet outer surface edge portions at said edge of said stack being relatively non-absorbent of said adhesive, whereby said mutually contacting sheet outer surface edge portions are not adhered together sufficiently to prevent easy separation of adjacent sets in said stack.

2. A stack of readily separable sets of paper sheets according to claim 1 in which at least one of said sets includes at least one inner sheet and two outer sheets, and in which said adhesive penetrates beneath the surface of said at least one set into the interior of the edge portion surfaces of said at least one inner sheet but not into the interior edge portions of said outer sheets.

3. A stack of readily separable sets of paper sheets according to claim 2 in which at least one of said sets includes two relatively hard outer sheets and at least one relatively soft inner sheet.

4. A stack of readily separable sets of paper sheets according to claim 3 in which at least one of said sets includes both relatively hard and relatively soft inner sheets so relatively positioned that relatively hard sheets are separated by relatively soft sheets.

5. A stack of readily separable sets of paper sheets according to claim 1 in which said adhesive comprises 20% dextrine, 60% water, 10% alcohol, 5% borax and 5% of china clay.

6. A stack of readily separable sets of paper sheets according to claim 1 in which said adhesive comprises 20% dextrine, 60% water, 10% alcohol, 5% borax and 5% low viscosity gum arabic with added alcohol.

7. A stack of readily separable sets of paper sheets according to claim 1 in which at least one of said sets comprises at least three sheets at least one of which has a Gurley densometer reading of more than 1,000 and is arranged with its grain direction parallel to the edge to which adhesive is applied, and at least two of the other sheets have Gurley densometer readings of less than 300 and are arranged with their grain direction parallel to the edge to which adhesive is applied.

8. A stack of readily separable sets of paper sheets according to claim 1 in which at least some of said mutually contacting inner surfaces are relatively absorbent, and in which said mutually contacting outer surfaces are relatively non-absorbent.

9. A stack of readily separable sets of paper sheets according to claim 8 in which at least one of said sets is assembled to include two outer sheets and a plurality of inner sheets, mutually contacting pairs of sheets throughout said at least one of said sets comprising relatively absorbent and relatively non-absorbent contacting surfaces, all of said inner sheets having a relatively absorbent surface.

10. A stack of readily separable sets of paper sheets according to claim 9 in which said relatively absorbent surfaces are provided by sheets having a grain direction which is normal to the sheet edge to which adhesive is applied, and in which said relatively nonabsorbent surfaces are provided by sheets having a grain direction which is parallel to the sheet edge to which adhesive is applied.

11. A stack of readily separable sets of paper sheets according to claim 10 in which the densities of said inner and outer sheets are substantially the same.

12. In a method of forming a stack of readily separable sets of paper sheets, each set including a plurality of sheets edge-adhered together, the steps of stacking sheets with mutually contacting sheet inner surfaces within each set and mutually contacting sheet outer surfaces on the outside of each two adjacent sets in the stack; and applying adhesive to an edge of said stack, the edge portions of said sheets at the edge of said stack to which adhesive is to be applied being free of previously applied coating of adhesive resist and inherently having such relative absorbency characteristics that said adhesive will effectively adhere said mutually contacting sheet inner surfaces together and will not adhere said mutually contacting sheet outer surfaces together sufficiently to prevent easy separation of adjacent sets in said stack.

13. A method according to claim 12 in which at least one of said sets includes at least one inner sheet and two outer sheets, and in which said adhesive penetrates beneath the surface of said at least one set into the interior of the edge portion surfaces of said at least one inner sheet but not into the interior edge portions of said outer sheets.

14. A method according to claim 13 in which at least one of said sets includes two relatively hard outer sheets and at least one relatively soft inner sheet.

15. A method according to claim 14 in which at least one of said sets includes both relatively hard and relative- 1y soft inner sheets so relatively positioned that relatively hard sheets are separated by relatively soft sheets.

16. A method according to claim 14 in which at least one of said sets comprises at least four sheets, all the inner sheets being relatively soft as compared to the relatively hard outer sheets.

17. A method according to claim 12 in which said adhesive comprises 20% dextrine, 60% water, 10% alcohol, 5% borax and 5% china clay.

18. A method according to claim 12 in which said adhesive comprises 20% dextrine, 60% water, alcohol, 5% iborax and 5% of a mixture of low viscosity gum arabic with alcohol and china clay.

19. A method according to claim 12 in which at least one of said sets comprises at least three sheets at least one of which has a Gurley densometer reading of more than 1,000 and is arranged with its grain direction parallel to the edge to which adhesive is applied, and at least two of the other sheets have Gurley densometer readings of less than 300 and are also arranged with their grain direction parallel to the edge to which adhesive is applied.

20. A method according to claim 12 in which at least one of said sets is assembled to include two outer sheets and a plurality of inner sheets, mutually contacting pairs of sheets throughout said at least one of said sets comprising relatively absorbent and reltively nonabsorbent contacting surfaces, all of said inner sheets having a relatively absorbent surface.

21. A method according to claim 20 in which said relatively absorbent surfaces are provided by sheets having a grain direction which is normal to the sheet edge to which adhesive is applied, and in which said relatively non-absorbent surfaces are provided by sheets having a grain direction which is parallel to the sheet edge to which adhesive is applied.

22. A method according to claim 21 in which the densities of said inner and outer sheets are substantially the same.

References Cited UNITED STATES PATENTS Re. 22,007 1/1942 Stevens 282--22 1,918,246 7/1933 Burrows l6l55 X 2,477,344 7/1949 Neumann 106214 X 2,55 8,405 6/1951 Weinstein 28222 2,589,202 3/1952 Newman 156-305 2,930,632 3/1960 Winders et al 156-305 2,968,336 1/1961 Martin et a1 156305 FOREIGN PATENTS 503,224 3/1939 Great Britain.

OTHER REFERENCES Handbook of Adhesives, Skeist, 1962, pp. 479, 442.

EARL M. BERGERT, Primary Examiner.

R. KILLWORTH, Assistant Examiner. 

